[libdrm,v3] drm: add drmGet(Master|Render)NameFrom(Render|Master)FD functions

Commit Message

Emil Velikov March 7, 2015, 12:58 a.m. UTC

Currently most places assume reliable master <> render node mapping.
Although this may work in some cases, it is not correct.

Add a couple of helpers that hide the details and provide the name of
the master/render device name, given an render/master FD.

v2:
 - Rename Device and Primary to Master (aka the /dev/dri/cardX device).
 - Check for the file via readdir_r() rather than stat().
 - Wrap the check into a single function.
 - Return NULL for non-linux platforms.

v3:
 - Don't segfault if name is NULL.
 - Update function names, as suggested by Frank Binns.

Cc: Frank Binns <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: David Herrmann <[e-mail]>
Signed-off-by: Emil Velikov <[e-mail]>
Reviewed-by: Frank Binns <[e-mail]>
---

Hi all,

I'm planning to push this Monday afternoon. If you have any comments or 
suggestions please go ahead.

Cheers,
Emil


 xf86drm.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 xf86drm.h |  3 +++
 2 files changed, 87 insertions(+)

Comments

Emil Velikov March 7, 2015, 1:08 a.m. UTC | #1

On 7 March 2015 at 00:58, Emil Velikov <[e-mail]> wrote:
> Currently most places assume reliable master <> render node mapping.
> Although this may work in some cases, it is not correct.
>
> Add a couple of helpers that hide the details and provide the name of
> the master/render device name, given an render/master FD.
>
> v2:
>  - Rename Device and Primary to Master (aka the /dev/dri/cardX device).
>  - Check for the file via readdir_r() rather than stat().
>  - Wrap the check into a single function.
>  - Return NULL for non-linux platforms.
>
> v3:
>  - Don't segfault if name is NULL.
>  - Update function names, as suggested by Frank Binns.
And seemingly I've forgot to update the patch summary to reflect the
change. I'll do so before pushing

-Emil

Patch

diff --git a/xf86drm.c b/xf86drm.c
index e117bc6..194cd35 100644
--- a/xf86drm.c
+++ b/xf86drm.c
@@ -40,6 +40,8 @@ 
 #include <string.h>
 #include <strings.h>
 #include <ctype.h>
+#include <dirent.h>
+#include <stddef.h>
 #include <fcntl.h>
 #include <errno.h>
 #include <signal.h>
@@ -522,6 +524,20 @@  static int drmGetMinorType(int minor)
     }
 }
 
+static const char *drmGetMinorName(int type)
+{
+    switch (type) {
+    case DRM_NODE_PRIMARY:
+        return "card";
+    case DRM_NODE_CONTROL:
+        return "controlD";
+    case DRM_NODE_RENDER:
+        return "renderD";
+    default:
+        return NULL;
+    }
+}
+
 /**
  * Open the device by bus ID.
  *
@@ -2736,3 +2752,71 @@  int drmPrimeFDToHandle(int fd, int prime_fd, uint32_t *handle)
 	return 0;
 }
 
+static char *drmGetMinorNameForFD(int fd, int type)
+{
+#ifdef __linux__
+	DIR *sysdir;
+	struct dirent *pent, *ent;
+	struct stat sbuf;
+	const char *name = drmGetMinorName(type);
+	int len;
+	char dev_name[64], buf[64];
+	long name_max;
+	int maj, min;
+
+	if (!name)
+		return NULL;
+
+	len = strlen(name);
+
+	if (fstat(fd, &sbuf))
+		return NULL;
+
+	maj = major(sbuf.st_rdev);
+	min = minor(sbuf.st_rdev);
+
+	if (maj != DRM_MAJOR || !S_ISCHR(sbuf.st_mode))
+		return NULL;
+
+	snprintf(buf, sizeof(buf), "/sys/dev/char/%d:%d/device/drm", maj, min);
+
+	sysdir = opendir(buf);
+	if (!sysdir)
+		return NULL;
+
+	name_max = fpathconf(dirfd(sysdir), _PC_NAME_MAX);
+	if (name_max == -1)
+		goto out_close_dir;
+
+	pent = malloc(offsetof(struct dirent, d_name) + name_max + 1);
+	if (pent == NULL)
+		 goto out_close_dir;
+
+	while (readdir_r(sysdir, pent, &ent) == 0 && ent != NULL) {
+		if (strncmp(ent->d_name, name, len) == 0) {
+			free(pent);
+			closedir(sysdir);
+
+			snprintf(dev_name, sizeof(dev_name), DRM_DIR_NAME "/%s",
+				 ent->d_name);
+			return strdup(dev_name);
+		}
+	}
+
+	free(pent);
+
+out_close_dir:
+	closedir(sysdir);
+#endif
+	return NULL;
+}
+
+char *drmGetPrimaryDeviceNameFromFd(int fd)
+{
+	return drmGetMinorNameForFD(fd, DRM_NODE_PRIMARY);
+}
+
+char *drmGetRenderDeviceNameFromFd(int fd)
+{
+	return drmGetMinorNameForFD(fd, DRM_NODE_RENDER);
+}
diff --git a/xf86drm.h b/xf86drm.h
index afd38a1..40c55c9 100644
--- a/xf86drm.h
+++ b/xf86drm.h
@@ -749,6 +749,9 @@  extern int drmGetNodeTypeFromFd(int fd);
 extern int drmPrimeHandleToFD(int fd, uint32_t handle, uint32_t flags, int *prime_fd);
 extern int drmPrimeFDToHandle(int fd, int prime_fd, uint32_t *handle);
 
+extern char *drmGetPrimaryDeviceNameFromFd(int fd);
+extern char *drmGetRenderDeviceNameFromFd(int fd);
+
 #if defined(__cplusplus) || defined(c_plusplus)
 }
 #endif